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1.
  • Grigoriev, Anton, et al. (författare)
  • Electron transport in stretched monoatomic gold wires
  • 2006
  • Ingår i: Physical Review Letters. - 0031-9007. ; 97:23, s. 236807
  • Tidskriftsartikel (refereegranskat)abstract
    • The conductance of monoatomic gold wires containing 3-7 gold atoms has been obtained from ab initio calculations. The transmission is found to vary significantly depending on the wire stretching and the number of incorporated atoms. Such oscillations are determined by the electronic structure of the one-dimensional (1D) part of the wire between the contacts. Our results indicate that the conductivity of 1D wires can be suppressed without breaking the contact.
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2.
  • Laukkanen, P., 0, et al. (författare)
  • Anomalous bismuth-stabilized (2x1) reconstructions on GaAs(100) and InP(100) surfaces
  • 2008
  • Ingår i: Physical Review Letters. - 0031-9007. ; 100:8, s. 086101
  • Tidskriftsartikel (refereegranskat)abstract
    • First-principles phase diagrams of bismuth-stabilized GaAs- and InP(100) surfaces demonstrate for the first time the presence of anomalous (2 x 1) reconstructions, which disobey the common electron counting principle. Combining these theoretical results with our scanning-tunneling-microscopy and photoemission measurements, we identify novel (2 x 1) surface structures, which are composed of symmetric Bi-Bi and asymmetric mixed Bi-As and Bi-P dimers, and find that they are stabilized by stress relief and pseudogap formation.
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3.
  • Laukkanen, P., et al. (författare)
  • Bismuth-stabilized c(2X6) reconstruction on a InSb(100) substrate:
  • 2010
  • Ingår i: Physical Review B. - 1098-0121. ; 81:3
  • Tidskriftsartikel (refereegranskat)abstract
    • By means of scanning tunneling microscopy/spectroscopy (STM/STS), photoelectron spectroscopy, and first-principles calculations, we have studied the bismuth (Bi) adsorbate-stabilized InSb(100) substrate surface which shows a c(2X6) low-energy electron diffraction pattern [thus labeled Bi/InSb(100)c(2X6) surface] and which includes areas with metallic STS curves as well as areas with semiconducting STS curves. The first-principles phase diagram of the Bi/InSb(100) surface demonstrates the presence of the Bi-stabilized metallic c(2X6) reconstruction and semiconducting (4X3) reconstruction depending on the chemical potentials, in good agreement with STS results. The existence of the metallic c(2X6) phase, which does not obey the electron counting model, is attributed to the partial prohibition of the relaxation in the direction perpendicular to dimer rows in the competing reconstructions and the peculiar stability of the Bi-stabilized dimer rows. Based on (i) first-principles phase diagram, (ii) STS results, and (iii) comparison of the measured and calculated STM and photoemission data, we show that the measured Bi/InSb(100)c(2X6) surface includes metallic areas with the stable c(2X6) atomic structure and semiconducting areas with the stable (4X3) atomic structure.
4.
  • Lång, J. J. K., et al. (författare)
  • Tin-stabilized (1 x 2) and (1 x 4) reconstructions on GaAs(100) and InAs(100) studied by scanning tunneling microscopy, photoelectron spectroscopy, and ab initio calculations
  • 2011
  • Ingår i: Surface Science. - 0039-6028. ; 605:9-10, s. 883-888
  • Tidskriftsartikel (refereegranskat)abstract
    • Tin (Sn) induced (1 x 2) reconstructions on GaAs(100) and InAs(100) substrates have been studied by low energy electron diffraction (LEED), photoelectron spectroscopy, scanning tunneling microscopy/spectroscopy (STM/STS) and ab initio calculations. The comparison of measured and calculated STM images and surface core-level shifts shows that these surfaces can be well described with the energetically stable building blocks that consist of Sn-III dimers. Furthermore, a new Sn-induced (1 x 4) reconstruction was found. In this reconstruction the occupied dangling bonds are closer to each other than in the more symmetric (1 x 2) reconstruction, and it is shown that the (1 x 4) reconstruction is stabilized as the adatom size increases.
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5.
  • Punkkinen, M. P. J., et al. (författare)
  • Bismuth-stabilized (2x1) and (2x4) reconstructions on GaAs(100) surfaces : Combined first-principles, photoemission, and scanning tunneling microscopy study
  • 2008
  • Ingår i: Physical Review B. Condensed Matter and Materials Physics. - 1098-0121. ; 78:19
  • Tidskriftsartikel (refereegranskat)abstract
    • Bismuth adsorbate-stabilized (2x1) and (2x4) reconstructions of the GaAs(100) surfaces have been studied by first-principles calculations, valence-band and core-level photoelectron spectroscopies, and scanning tunneling microscopy. It is demonstrated that large Bi atom size leads to the formation of the pseudogap at the Fermi energy and to the lower energy of an adsorbate-derived surface band, which contributes to the stabilization of the exceptional Bi/GaAs(100)(2x1) reconstruction. It is proposed that the Bi/GaAs(100)(2x4) reconstructions include asymmetric mixed Bi-As dimers, in addition to the Bi-Bi dimers. Based on the calculations, we solve the atomic origins of the surface core-level shifts (SCLSs) of the Bi 5d photoemission spectra from the Bi/GaAs(100)(2x4) surfaces. This allows for resolving the puzzle related to the identification of two SCLS components often found in the measurements of the Bi 5d and Sb 4d core-level emissions of the Bi/III-V and Sb/III-V(100)(2x4) surfaces. Finally, the reason for the absence of the common (2x4)-beta 2 structure and additional support for the stability of the (2x1) structure on the Bi/III-V(100) surfaces are discussed in terms of Bi atom size and subsurface stress.
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6.
  • Andersson, D. A., et al. (författare)
  • Redox properties of CeO2-MO2 MO2 (M=Ti, Zr, Hf or Th) solid solutions from first principles calculations
  • 2007
  • Ingår i: Applied Physics Letters. - 0003-6951. ; 90:3, s. 031909
  • Tidskriftsartikel (refereegranskat)abstract
    • The authors have used density functional theory calculations to investigate how the redox thermodynamics and kinetics of CeO2 are influenced by forming solid solutions with TiO2, ZrO2, HfO2, and ThO2. Reduction is facilitated by dissolving TiO2 (largest improvement), HfO2, or ZrO2 (least improvement), while ThO2 makes reduction slightly more difficult. The migration barrier is much lower in the neighborhood of a Ti (largest decrease), Hf, or Zr (least decrease), while the binding energy of solute ions and vacancies increases in the same sequence. They rationalize the properties of ceria solid solutions in terms of defect cluster relaxations.
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7.
  • Andersson, Martin, et al. (författare)
  • Heterogeneous Distributions of Firms Sustained by Innovation Dynamics-A Model with Empirical Illustrations and Analysis
  • 2012
  • Ingår i: Journal of Industry, Competition and Trade. - 1566-1679. ; 12:2, s. 239-263
  • Tidskriftsartikel (refereegranskat)abstract
    • This paper develops a framework of innovation dynamics to appreciate observed heterogeneity of firm size distributions, in which dynamics refer to exit and entry of product varieties and variety markets of individual firms. The analysis is based on a model of variety-triplets where every such triplet in the economy is identified by a unique combination of a variety, destination and firm. New variety triplets are introduced by innovating firms in a quasi-temporal setting of monopolistic competition. Ideas for variety-triplets arrive to firms according to a firm-specific and state dependent Poisson process, whereas variety triplets exit according to a destination-specific Poisson process. The empirical analysis employs a detailed firm-level data base which provides information about all variety triplets. Firm size is measured by a firm's number of variety triplets. The empirical results are compatible with the model predictions of (i) a persistent distribution of firm sizes, (ii) frequent events of exit and entry, and (iii) state dependent entry, where a state may be given by each firm's composition of triplets and/or other firm attributes.
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8.
  • Belonoshko, A. B., et al. (författare)
  • Xenon melting: : Density functional theory versus diamond anvil cell experiments
  • 2006
  • Ingår i: Physical Review B Condensed Matter. - 0163-1829. ; 74, s. 054114
  • Tidskriftsartikel (refereegranskat)abstract
    • We performed two-phase ab initio density functional theory based molecular dynamics simulations of Xe melting and demonstrated that, contrary to claims in the recent literature, the pressure dependence of the Xe melting curve is consistent with the corresponding-states theory as well as with the melting curve obtained earlier from classical molecular dynamics with a Xe pair potential. While at low pressure the calculated melting curve is in perfect agreement with reliable experiments, our calculated melting temperatures at higher pressures are inconsistent with those from the most recent diamond anvil cell experiment. We discuss a possible explanation for this inconsistency.
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9.
  • Bleskov, I. D., et al. (författare)
  • Ab initio calculations of elastic properties of Ru1-xNixAl superalloys
  • 2009
  • Ingår i: Applied Physics Letters. - 0003-6951. ; 94:16
  • Tidskriftsartikel (refereegranskat)abstract
    • Ab initio total energy calculations based on the exact muffin-tin orbitals method, combined with the coherent potential approximation, have been used to study the thermodynamical and elastic properties of substitutional refractory Ru1-xNixAl alloys. We have found that the elastic constants C' and C11 exhibit pronounced peculiarities near the concentration of about 40 at. % Ni, which we ascribe to electronic topological transitions. Our suggestion is supported by the Fermi surface calculations in the whole concentration range. Results of our calculations show that one can design Ru-Ni-Al alloys substituting Ru by Ni (up to 40 at. %) with almost invariable elastic constants and reduced density.
10.
  • Dubrovinskaia, N., et al. (författare)
  • Beating the Miscibility Barrier Between Iron Group Elements and Magnesium by High-Pressure Alloying
  • 2005
  • Ingår i: Physical review letters / publ. by the American Physical Society. ; 86, s. 245502-245513
  • Tidskriftsartikel (refereegranskat)abstract
    • Iron and magnesium are almost immiscible at ambient pressure. The low solubility of Mg in Fe is due to a very large size mismatch between the alloy components. However, the compressibility of Mg is much higher than that of Fe, and therefore the difference in atomic sizes between elements decreases dramatically with pressure. Based on the predictions of ab initio calculations, we demonstrate in a series of experiments in a multianvil apparatus and in electrically and laser-heated diamond anvil cells that high pressure promotes solubility of magnesium in iron. At the megabar pressure range, more than 10 at. % of Mg can dissolve in Fe and then the alloy can be quenched to ambient conditions. A generality of the concept of high-pressure alloying between immiscible elements is demonstrated by its application to two other Fe group elements, Co and Ni.
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